tailieunhanh - Chapter 070. Nutritional Requirements and Dietary Assessment (Part 2)

Water For adults, – mL water per kcal of energy expenditure is sufficient under usual conditions to allow for normal variations in physical activity, sweating, and solute load of the diet. Water losses include 50–100 mL/d in the feces, 500–1000 mL/d by evaporation or exhalation, and, depending on the renal solute load, ≥1000 mL/d in the urine. If external losses increase, intakes must increase accordingly to avoid underhydration. Fever increases water losses by approximately 200 mL/d per °C; diarrheal losses vary but may be as great as 5 L/d with severe diarrhea. Heavy sweating and vomiting also increase water. | Chapter 070. Nutritional Requirements and Dietary Assessment Part 2 Water For adults mL water per kcal of energy expenditure is sufficient under usual conditions to allow for normal variations in physical activity sweating and solute load of the diet. Water losses include 50-100 mL d in the feces 500-1000 mL d by evaporation or exhalation and depending on the renal solute load 1000 mL d in the urine. If external losses increase intakes must increase accordingly to avoid underhydration. Fever increases water losses by approximately 200 mL d per C diarrheal losses vary but may be as great as 5 L d with severe diarrhea. Heavy sweating and vomiting also increase water losses. When renal function is normal and solute intakes are adequate the kidneys can adjust to increased water intake by excreting up to 18 L d of excess water Chap. 334 . However obligatory urine outputs can compromise hydration status when there is inadequate intake or when losses increase in disease or kidney damage. Infants have high requirements for water because of their large ratio of surface area to volume the limited capacity of the immature kidney to handle high renal solute loads and their inability to communicate their thirst. During pregnancy 30 mL d additional water is needed. During lactation milk production increases water requirements by approximately 1000 mL d or 1 mL for each mL of milk produced. Special attention must be paid to the water needs of the elderly who have reduced total body water and blunted thirst sensation and may be taking diuretics. Other Nutrients See Chap. 71 for a detailed description of vitamins and trace minerals. Dietary Reference Intakes and Recommended Dietary Allowances Fortunately human life and well-being can be maintained within a fairly wide range for most nutrients. However the capacity for adaptation is not infinite too much of a nutrient as well as too little may have adverse effects on health. Therefore quantitative benchmark recommendations .